Various plant root materials have been used as stop-leak additives since the early 1950s. For example, U.S. Pat. Re. No. 24,094 (based on U.S. Pat. No. 2,580,719) provides a stop-leak product containing ground plant roots and a water soluble cutting oil. This formulation, while effective in stopping leaks in an automobile radiator system, has significant drawbacks. Most importantly, this stop-leak product must be essentially anhydrous. If water is present in the formulation, the plant root material agglomerates and settles to the bottom of the container, thereby rendering it essentially unsuitable for its intended purpose. Thus, traces of water present in the formulation (whether in the formulation as originally manufactured or entering the formulation during storage) could significantly reduce the effective storage life of the product. Once the plant root material agglomerates and settles to the bottom of the container it cannot be readily dispersed in the soluble oil and, even if dispersed, it may not be effective in stopping leaks.
Several approaches have been taken to overcome the problems associated with the water sensitivity of the ground plant root and soluble oil formulations. U.S. Pat. No. 2,935,189 describes a packaging system whereby the plant root powder is mixed with soluble oil and then compressed and extruded as pellets. The pellets are then coated with polyvinyl alcohol to act as a binder and protective coating. The binder coating, about three or four mils thick, is soluble in water but insoluble in oil. The binder-coated pellets are then placed in a suitable container containing oil. In theory, the binder coating protects the active ingredients until the container contents are placed in a leaking radiator at which time the water in the radiator dissolves the binder coating. The released plant root powder is then available to stop the leak. Unfortunately, water present in the container or entering the container over time can attack or dissolve the binder coating and reach the water sensitive components. Thus, this approach reduces but does not eliminate problems associated with water sensitivity of the plant root stop-leak products. Stop-leak pellets produced in this manner still lack a sufficiently long shelf life. In addition, the volume of soluble oil required to produce and package these binder-coated pellets is significant and can, therefore, present a significant environmental problem for the use and disposal of such products. U.S. Pat. No. 3,034,998 describes a similar stop-leak formulation containing ground nut shells, castor oil, and polyvinyl alcohol. And U.S. Pat. No. 3,616,896 describes an elaborate package whereby one compartment contains the stop-leak material (i.e., plant root powder) and a second compartment contains an antifreeze liquid. The contents of two compartments are mixed together just prior to adding the formulation to a cooling system at the point of use.
Stop-leak pellets prepared by the process of U.S. Pat. No. 2,935,189 or by similar processes are currently available in the marketplace for adding to the cooling system of an automobile. The two-compartment system of U.S. Pat. No. 3,616,896 does not appear to have been widely accepted or used in the marketplace. The stop-leak pellets with the binder coating, although an improvement over previous stop-leak products, have not eliminated the problems associated with water sensitivity and have increased the environmental problems associated with use and ultimate disposal of such products.
Others have attempted to solve the water sensitivity problems associated with the ground plant root materials by preparing, storing, and selling the stop-leak product in the form of dry pellets. U.S. Pat. Nos. 3,322,548, 4,348,235, and 4,662,940 describe stop-leak formulations in the form of a dry pellet containing ginger rhizome flour, ground nut shells, and various other components. One or two of the dry pellets were to be added to the automobile system. Consumer acceptance of the dry pellet product has not been high.
Other stop-leak products have been developed using active ingredients other than the plant root materials. For example, U.S. Pat. No. 3,692,549 describes a stop-leak formulation containing flax meal, graphite powder, and aluminum powder as the active ingredients. And U.S. Pat. Nos. 4,439,561 and 4,524,158 use fibrillated fibers as the active ingredient. Preferred fibrillated fibers included synthetic polymers such as poly(imino-1,4-phenyleneiminoterephthaloyl). And U.S. Pat. No. 4,872,911 describes the use of tri-dimensional cross-linked superabsorbent hydrogels. These active ingredients and the stop-leak formulations containing them are generally more expensive than stop-leak products containing readily available plant root powders.
It is desirable, therefore, to provide stop-leak formulations containing plant root materials as the active ingredient and which are not water sensitive. It is also desirable to provide a stop-leak formulation with a long shelf life. It is also desirable to provide a stop-leak material which is essentially oil free. The stop-leak formulations of the present invention satisfy these requirements.